RSV vaccination in pregnant women could change the rules of the disease

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For six decades, there has been no approved vaccine for one of the most common causes of severe illness in infants, young children and the elderly: RSV (respiratory syncytial virus). so far.

2023 is a year of significant progress, with multiple vaccines and treatments approved. On Monday, the U.S. Food and Drug Administration (FDA) approved a vaccine for pregnant women, the first of its kind against RSV, to protect vulnerable infants.

One of the scientists responsible for the discovery is Jason McLellan, a professor in the Department of Molecular Biosciences at UT Austin. McClellan said that although most people will be repeatedly infected with RSV throughout their lives, it only poses a strong threat to certain groups.

“RSV can cause severe disease in young children and the elderly,” he said. “For a healthy adult, it’s a bad cold.”

According to the U.S. Centers for Disease Control and Prevention, RSV is the leading cause of hospitalization in infants. The agency estimates that as many as 80,000 children under the age of 5 are hospitalized with RSV each year. Each year, 60,000 to 160,000 older adults are hospitalized with the virus and 6,000 to 10,000 die.

Despite these sobering statistics, the severity of RSV is not always understood, McClellan said.

“Most of the time, when people get RSV, they don’t know it, and it’s classified as a flu-like illness,” he explained. “It wasn’t until the last decade or so, through RSV-specific testing, that it was recognized that many respiratory hospitalizations and deaths were actually caused by RSV.”

a breakthrough

A spike in cases during the 2022 winter RSV season has also raised awareness of the common virus, McLellan said. Coincidentally, this timing coincides with a flurry of activity in the testing and development of vaccines and treatments.

At the end of last year, the clinical trials of vaccines by various pharmaceutical companies entered the final stage. In May, GSK’s Arexvy vaccine for adults aged 60 and older became the first RSV vaccine approved by the FDA. Not long after, Pfizer’s Abrysvo was approved for use in older adults. On Monday, Abrysvo was also approved for use in pregnant women between 32 and 36 weeks’ gestation.

Although these vaccines crossed the finish line around the same time, they are all based on decades of work.

“RSV was first isolated from chimpanzees in 1956, and since then many researchers have spent decades trying to understand basic virology,” McClellan explained. “How a virus enters a cell, what its proteins are, how it causes disease and how vaccines are made.”

Several factors contribute to the lengthy time it takes for an effective vaccine to be approved. One of these was a failed attempt to develop an RSV vaccine for infants in the 1960s, which ended up making vaccinated children more likely to become seriously ill. Two people died. The tragedy has made researchers especially wary of RSV vaccines for infants, McClellan said.

Also, technology has to keep up. He and his colleagues at the National Institutes of Health played a key role in this breakthrough by developing a new method to engineer and stabilize the proteins that certain viruses use to enter cells. The breakthrough is also critical to the development of a COVID-19 vaccine, work for which McClellan is probably best known.

What now?

Pfizer’s vaccine still needs approval from the U.S. Centers for Disease Control and Prevention (CDC) for use in pregnant women. Once approved, the FDA and CDC will continue to monitor the vaccine’s effectiveness.

Looking ahead to the fall and winter RSV seasons, the CDC is recommending that infants younger than eight months be treated with a new monoclonal antibody, which may help prevent infection. With this treatment, babies receive injections of antibodies, which provide protection until they are old enough to mount their own immune response.

Meanwhile, McClellan and colleagues in his UT lab were studying other viruses, such as human metapneumovirus, another RSV-like virus that causes severe disease in children and the elderly. It also focuses on other pathogens that could cause major outbreaks in the future.

“Vaccine development takes a long time,” he said. “There are already a lot of funders starting to invest in research on how to make vaccines against different virus families. If there is a pandemic or a pandemic in the future, we are ready.”